Chemical, Radiological, Biological and Nuclear Defense (CRBN) is a high priority of the Army and National Security due to rogue states and the rise of terrorist organizations that are technologically sophisticated, well-financed and committed to inflicting damage on U.S. interests and personnel. The increased threat of chemical and biological agent attack in various military theaters combined with the possibility of terrorist attacks on the general public has led the inventors hereof to evaluate protective equipment for military and civil defense. Battlefield chemical protective materials are sought that do not just serve as simple barriers to incoming threats, but can reactively decontaminate the threat agents so as not to impede the mission at hand.
It is known that an extremely small amount of a CWA, such as a nerve agent, can affect the transmission of chemical nerve impulses in humans leading to death soon after exposure. Because of this toxicity protection against CWAs, biological weapons and toxic industrial chemicals (TICs) requires capture efficiency greater than about 99.97 percent combined with sufficient decontaminating capabilities.
There are several known decontaminating technologies that have been developed to degrade CWAs and TICs. However, to date, there is no single solution to provide comprehensive protection for personnel working in both dry and wet environments.
One known chemical method typically employed to degrade stockpiles of CWAs uses caustic salts at high temperatures. However, such a method often generates side-reactions which can reverse to form the original toxic chemical agents. To overcome these shortcomings inorganic catalysts have been used to degrade CWAs and TICs because they are more robust but have low catalytic activity. More recently biological catalysts have been developed which rapidly and safely decontaminate CWAs or TICs but have limited life spans because of their fragile nature.
Enzymes, such as organophosphate degrading enzymes (OPH, OPAA), and the like, are reported to be efficient catalytic materials that effectively degrade CWAs and TICs. These enzymes denature rapidly when in solution and their performance is based solely on limited temperature and pH ranges. To mitigate these shortcomings the enzymes need to be immobilized, which will allow the system to be reusable, recyclable and recoverable while maintaining chemical activity towards all types of CWAs and TICs in both dry and wet environments.
Several known methods for immobilization of enzymes often rely on stabilizing the enzymes during the deposition phase and retard their deactivation upon prolonged exposure to stressful conditions. One known method relies on a covalent chemistry approach in which the reaction conditions use organic solvents. However, such a technique causes a major loss of enzyme activity. In one example, a research group developed a polyurethane nanosponge to degrade toxins. However, most of the enzymes incorporated into the sponge were eventually rendered inactive during the polymerization process.
To avoid such a loss of activity of the enzymes, one known layer-by-layer (LBL) method provides a versatile platform for the fabrication of multifunctional bio-materials utilizing catalytic enzymes. A Naval Research Laboratory (NRL) research team has reported enzymes immobilized in polyelectrolyte multilayer assemblies capable of maintaining their catalytic activity over long periods of time, e.g., greater than about 8 months. Fabricated OPH enzyme-bearing cotton cloths via layer-by-layer assembly preserved their hydrolytic activity against methyl parathion (MPT) within 5 minutes of exposure. The non-covalent method of the NRL team for incorporating enzymes helps tremendously in maintaining enzyme activity by protecting the enzyme from denaturizing. However, even this layer-by-layer approach has some distinct drawback. Many catalytic enzyme multilayers were shown to have limited activity towards their respective agents. This indicates only a limited amount of the enzyme, due to its amphoteric nature, was actually loaded onto the system.